A known system for treating exhaust gas passing through an exhaust system of a diesel engine comprises a diesel oxidation catalyst (DOC) associated with a diesel particulate filter (DPF). The combination of these two exhaust gas treatment devices promotes chemical reactions in exhaust gas and traps diesel particulate matter (DPM) as exhaust flows through the exhaust system from the engine, thereby preventing significant amounts of pollutants such as hydrocarbons, carbon monoxide, soot, SOF, and ash, from entering the atmosphere.
While an engine is running, the existence of certain conditions enables regeneration of a DPF to be initiated. Various techniques are available for developing temperatures sufficiently high to initiate regeneration and thereafter control on-going regeneration. Regeneration is essentially a chemical process that cleans a DPF by burning off trapped DPM. For any of various reasons, not all trapped DPM may be burned off by regeneration. Moreover, the burning of trapped DPM may contribute to the build-up of ash, a non-combustible particulate.
Consequently, it may be either necessary or desirable to occasionally use a physical or mechanical process, rather than a chemical process, to remove particulate matter, such as DPM and/or ash, from a DPF. The use of compressed air has been proposed as one way to remove the particulate matter.
Compressed air is an appropriate medium because it is readily available in service facilities and shops and it is environmentally friendly. Cleaning a DPF by compressed air has involved certain manual operations such as removing the actual filter module from a casing and manually manipulating a compressed air nozzle across a face of the module. Dislodged matter is ejected from an opposite face and collected in some type of collector for subsequent disposal.
When a DPF has been used to an extent where regeneration and mechanical cleaning are unable to sufficiently clean it, it must be replaced.
In light of this background, it is believed that improvements in the mechanical cleaning of diesel particulate filters would enjoy commercial acceptance. For example, a cleaning device and method that would minimize the amount of labor required would be beneficial. Likewise, a device and method that could clean a diesel particulate filter more thoroughly and that could extend the useful life of the filter would be desirable. The ability to satisfactorily clean a diesel particulate filter without having to remove the actual filter module from its casing also would have obvious advantages.
An improvement that would allow an engine to keep running with the exhaust treatment system remaining effective to trap DPM during on-going mechanical cleaning could also be considered desirable.